Currently, input devices such as mice, keyboards, sensor panels, touch screens and the like are being widely used in electronic products such as computers, PADs, mobile phones and the like. Especially, touch screens, due to easy operation and continuously reduced cost, have become more and more popular.
Relative to the prior art (e.g., traditional type and OGS) in which a touch panel is provided on a liquid crystal panel, a technique in which a touch panel function is integrated in a liquid crystal panel becomes increasingly prevailing. Integration of a touch panel and a liquid crystal panel includes “in-cell” technique and “on-cell” technique. The in-cell technique refers to a method in which a touch panel function is embedded into pixel units of a liquid crystal panel. The on-cell technique refers to a method in which a touch panel function is embedded between a color filter substrate and a polarizer film. By integrating a touch panel part, which originally was provided externally, with a liquid crystal panel, a panel can be implemented to be thin and light in weight. In addition, in the prior art in which a touch panel is provided outside a liquid crystal panel, a physical space exists between the liquid crystal panel and the touch panel, and therefore, light from outside and the like may be reflected between an upper surface of the liquid crystal panel and a lower surface of the touch panel, resulting in deteriorated visibility in bright outdoor environments. If the external touch panel part can be integrated with the liquid crystal panel, the phenomenon of deteriorated visibility in the outdoors can be suppressed.
The in-cell technique fails to achieve progress in practicality, as it is difficult to ensure yield rate and display performance. This is mainly because a touch sensor needs to be embedded inside each pixel unit on a TFT array substrate. For this purpose, it is necessary to adopt complex semiconductor manufacturing process, which becomes a stumbling block to the improvement of the yield rate. Further, embedding the touch sensor in the pixel may reduce an area portion that can be used for displaying, thus resulting in deteriorated picture quality.